Magnetic resonance imaging in children with sickle cell disease--detecting alterations in the apparent diffusion coefficient in hips with avascular necrosis.

BACKGROUND: Avascular necrosis (AVN) is a common morbidity in children with sickle cell disease (SCD) that leads to pain and joint immobility. However, the diagnosis is often uncertain or delayed.
OBJECTIVE: To examine the ability of apparent diffusion coefficient (ADC) measurements on diffusion-weighted imaging to detect AVN in children with SCD.
MATERIALS AND METHODS: ADC values were calculated at the hips of normal children (n = 19) and children with SCD who were either asymptomatic with no known previous hip disease (n = 13) or presented for the first time with clinical symptoms of hip pathology (n = 12). ADC values were compared for differences among groups with and without AVN using non-parametric statistical methods.
RESULTS: The ADC values were elevated in the hips of children with AVN (median ADC = 1.57 × 10(-3) mm(2)/s [95% confidence interval = 0.86-2.10]) and differed significantly in pairwise comparisons (all P < 0.05) from normal children (0.74 [0.46-0.98]), asymptomatic children with SCD (0.55 [0.25-0.85]), and SCD children who had symptoms referable to their hips but did not show findings of hip AVN on conventional MRI or radiographs (0.46 [0.18-0.72]).
CONCLUSION: Children with sickle cell disease have elevated apparent diffusion coefficient values in their affected hips on initial diagnosis of avascular necrosis.